Technical Field
Described herein are latching devices to control relative speed between members. More specifically, latching devices are described where relative speed of movement of the members are in part controlled or reduced via eddy current formation and in part controlled or relative motion stopped via a latch arrangement.
Description of the Related Art
Eddy current formation may be used in a variety of ways to adjust the speed of rotation of a member. Various apparatus exist, for example in abseiling, to control the descent of a climber or for example, in personal protective equipment scenarios to prevent an injury causing fall. Other applications that use eddy current generation are in controlling pay-out of line in trains, cable cars, zip line devices and roller coasters.
One art device is published as US2012/0055740. This device utilizes a rotor assembly with arms that move relative to the rotor. The arms themselves may be conductive or magnetic or may have conductive or magnetic members attached thereto. When a rotational force is applied to the rotor, the arms move outwards from a central axis via centrifugal force and into a magnetic (or conductive) field. As the arms move through the field, eddy currents are generated, the strength of which is dependent on the speed of rotation. As the speed of rotation reduces, the arms are drawn back towards the axis of rotation via springs and/or a reduced centrifugal force acting on the arms. This device is widely used and provides an excellent means of changing the relative speed of parts, however there is no mechanism to fully stop relative movement of the parts.
Applications where both slowing and completely stopping relative movement may be in a seat belt assembly used in vehicles or, alternatively in industrial personal fall safety devices to slow and halt a fall or a person from a height. Art designs of seat belts for example often use a centrifugal clutch arrangement where, on application of a high rate of extension of the belt or webbing from a spool, a weighted pivoting lever moves outward from the spool and engages a cam piece mounted to the spool housing, thereby jamming the lever against the housing and preventing further release of belt from the spool. This system is widely used and saves many lives, however it has no redundancy—if the lever fails the belt is of no use. Secondly, movement is a sudden stop with no graduated slowing effect leading to injuries at times where the belt passes across the wearer. The seat belt may also engage at times when unwanted such as when the vehicle is stopped or immobile. In an industrial fall safety product often worn for long periods of time, false activations are frustrating and tiring on the wearer. A common problem of these art devices with stopping latches is that there exist only small number of ways to tune the brake response leading to potential false activations.
As may be appreciated, providing a simple means of both slowing and fully stopping relative movement via both eddy current effects and a latch arrangement may be useful or at least it provides the public with a choice.
Further aspects and advantages of the latching devices will become apparent from the ensuing description that is given by way of example only.